1. Field of the Invention
The present disclosure generally relates to the field of semiconductor wafer processing technology. In particular, this disclosure relates to the design, fabrication, and manufacture of gallium arsenide (GaAs) integrated circuits.
2. Description of the Related Art
The use of GaAs substrates in the design and construction of integrated circuits has proven to have desirable effects. For example, GaAs substrates have been useful in achieving greater performance in power amplifier circuits. Typically, a GaAs integrated circuit will be used as a component in a larger circuit device or design. In order to be integrated into the circuit design, the GaAs integrated circuit is mechanically and electrically coupled to a printed circuit board for the circuit device. In other cases, the GaAs integrated device is mounted to other electronic devices.
The contact side of the GaAs integrated circuit is typically adhered to a contact pad on the device's printed circuit board. More particularly, the integrated circuit usually includes a gold layer which adheres to the printed circuit board pad using a conductive adhesive. Often, the GaAs substrate has vias which extend into or through the substrate for facilitating electrical flow vertically through the substrate. These vias are also coated with the gold conductive material. Depositing the gold layer is a time-consuming and relatively inefficient process. Also, gold is an expensive material, increasing the cost for GaAs integrated circuit products. Finally, gold has a relatively high dissolution rate in solder, and therefore is not able to be soldered to the pad of the device's printed circuit board. Instead, conductive adhesive is typically used to adhere the gold contact to the printed circuit board. The use of conductive adhesive requires an additional manufacturing step, and also requires the use of larger pads to accommodate adhesive overflow. However, even with these undesirable features, gold continues to be the standard metal used for a contact layer on GaAs integrated circuits, which significantly drives up the product cost especially in recent years due to the high price of gold.
Accordingly, there is a need for improved GaAs integrated circuits that are employ less costly component materials more efficiently manufactured. Furthermore, there is a need for improved methods for manufacturing such GaAs integrated circuits. As described herein, the inventors have developed systems and methods for fabricating GaAs integrated circuits using copper as the material for the contact layer. Nonetheless, as many devices continue to use gold as the contact material, there is often a need for use of shared equipment between copper-designated GaAs integrated circuits and gold-designated GaAs integrated circuits. Due to the deleterious effects attributable to cross-contamination between the two different contact materials, there is a need for improved systems and methods for processing GaAs integrated circuits having various contact materials. In particular, there is a need for improved methods to prevent cross-contamination between gold-designated GaAs integrated circuits and copper-designated GaAs integrated circuits throughout processing.